On Sun, 20 Nov 2005 08:11:41 +0600, Rijk van Geijtenbeek
In those software, the sequence in which the filter are listed
is the sequence in which they operate. And they give the option
of moving some particular filter up and down in the sequence.
Such a system (I know what you mean, I used The Bat before I switched to
Opera, and it had great filters) is only necessary if a message can only
end up in one filter. That filter had better be the one were you first
look for a specific message, so order is important. But with filters as
dynamic views into a single message database, where messages can turn up
in every view where they are relevant, the point is moot.
To V S Rawat and everyone interested.
There are two major conceptual approaches to mail sorting. Let's call them
procmail way and gmail way, after two well-known pieces of software.
Though the details vary, people want the same thing: their mail sorted
into several folders basing on some conditions specified upon messages.
Procmail way is more traditional, and for years it has been the only way
to sort mail. The well-known mail filtering tool, procmail, delivers
messages into different folders depending on what conditions does a
message satisfy. When a new message arrives, procmail checks the
conditions in order and takes appropriate actions (deliver to a folder,
redirect, discard etc). With each condition-action pair a flag is
associated which indicates whether to continue testing following
conditions after taking the action. This way, a message can, for example,
end up in several folders at once, which is sometimes the desired result.
Anyway, most procmail setups deliver each message to at most one folder,
which corresponds to the metaphor of physically sorting postage mail into
folders. When no conditions match a message, the default action takes
place, which is usually delivery to some kind of INBOX folder.
Gmail way was invented before Google, but it was Google's webmail service
which popularized this way of thinking. While procmail way is procedural
and is backed by a strong real-world metaphor, gmail way, being
declarative, gains popularity as searching and search-related technologies
become more and more important in the modern informational infrastructure.
In gmail way, a folder is not a location, it's a filter. Looking into a
folder is the same as doing a specific preconfigured search within all of
the saved mail. Creating a folder is the same as storing a search
bookmark. Unlike procmail way, in gmail way most setups have intersecting
filters, with one message ending up in multiple folders because it matches
several orthogonal conditions. While procmail can deliver a single message
into several folders, it's usually done by copying a message, but gmail
shows one message in multiple folders, so, for example, deleting a message
deletes it from the entire message database, not only from the current
folder. Of course, instant searching when viewing a folder's contents is
not necessarily how gmail way is actually implemented; the list of folders
a message belongs to can be calculated when the message arrives and
refreshed when the folder setup changes.
Procmail way and gmail way have their strengths and weaknesses. Which is
better depends on the way how the user thinks of his filters. If one
regards a folder as a PLACE where messages can be put to and removed from,
and just wants the computer to put the right messages into the right
folders for him, it's clearly procmail way. The advantage is that the user
can move messages between folders easily. The disadvantage is that when
the user changes the filtering setup, it doesn't affect the already-stored
messages, though it's often what the user wants (some software offers an
option to refilter already-stored mail when changing the configuration).
On the contrary, if the user thinks of a folder as a filtered VIEW into
his message archive, it's gmail way. The advantage of gmail way is that
added or modified filters immediately affect all previously stored mail.
The disadvantage is that messages usually cannot be manually moved between
Opera M2 implements something in between of these two. Each folder is a
place, and messages can be manually moved between folders, that's procmail
way. But instead of specifying a procmail-style ordered set of rules which
decide what messages go where, Opera associates a filtering condition with
each folder, that's gmail way. As a consequence, the filtering conditions
are unordered, unlike procmail-style rules, and a matched condition
doesn't prevent other filters from also being triggered. Only newly
received or created messages are automatically tested against the
conditions and sorted into the folders, that's a bit of procmail way, but
when creating or modifying a filter, there is an option to recheck every
message which is currently outside the filter, that's a bit of gmail way.
In fact, M2 has much of gmail in that it offers a broad selection of
built-in filters (or views): by contact, by label, by thread, by
There are three alternative paths that Opera M2 might take in its
1. Finally become procmail way by allowing filters to be ordered and
adding a checkbox "Stop processing filters after this one" to each filter.
This indeed would provide what V S Rawat and possibly others want, but it
would also make filter setup more complicated because a filter's contents
would become implicitly affected by other filters.
2. Finally become gmail way by giving up on the ability to manually add
and remove messages to and from filters. Instead, changes in a filter's
conditions would immediately affect what the user sees inside, as if it
was a search query.
3. Remain the hybrid as it is. Because Opera M2 exists this way for a long
time already, and there are many users who like it as it is and prefer it
to other MUAs, it seems to me the most probable course of action.
Opera M2 9.0 TP1 on Debian Linux 2.6.12-1-k7
* Origin: X-Man's Station at SW-Soft, Inc. [ICQ: 115226275]